A specific example of the invention will be described in the context of a device for the application of a preload between two members which are specifically inner and outer members constituted by a subsea wellhead and a conductor housing. One example of the prior art in relation to such devices is provided by our patents No. GB-2393990 and U.S. Pat. No. 7,025,145. In those patents there is an explanation of the need for the application of a preload between a wellhead and the conductor housing, i.e. for the reduction of fatigue damage.